Voice over Internet Protocol (VoIP) is fast expanding beyond the confines of computer-to-computer voice discussions and into the realm of wireless networks and cell-phone communications. Using a VoIP system, analog voice signals are converted into digital data packets and are then transmitted to their destination, such as a cell phone. However, the normal methods of transmitting packets of data may not be suitable for use in VoIP transmissions because of the unique requirements of a VoIP system, such as the need for a consistent orthogonality across the transmissions when scheduled in pairs in the same resource coupled with the delay constraints due to voice traffic. Without such a delay minimization, a conversation across a VoIP network may be interrupted and noticed by the user.
Additionally, as with almost everything related to networks, the capacity, or bandwidth required by VoIP transmissions becomes an issue. In general, the VoIP capacity can be seen as the maximum number of user equipments (UEs) that can be supported in a network so that no more than a specific number of users (for example 95%) are in outage with a defined packet loss limit (for example less than 2%) and a specific transmission delay limit (for example of less than 50 msec). To maximize this capacity, the area of scheduling the transmissions has seen much research.
This research has generally focused on two methods of scheduling: Persistent Scheduling (PS) and Semi-Persistent Scheduling (SPS). With persistent scheduling, a time-frequency resource for the original transmission is pre-allocated once for the entire voice burst, and this pre-allocation is generally defined by an applicable standard. Subsequent transmissions of the voice burst which might be needed if the original transmission is, for example, lost, are generally performed using a Hybrid Automatic Repeat reQuest (HARQ), which in a PS scheme is also predefined with a time-frequency resource using an applicable standard.
With a SPS scheme, the original transmission generally remains predefined, similar to the PS scheme. The retransmissions, however, are generally allocated dynamically just before the retransmission. As such, while the original transmission remains persistent, the retransmissions are performed more dynamically, such that it is semi-persistent. A SPS scheme, however, while being less restrictive than the PS scheme, also requires a much greater amount of overhead than the PS scheme in order to dynamically allocate resources.
One disadvantage of the prior art is that it does not deal with capacity loss that occurs from signals that terminate early but are in a PS scheme, thereby wasting the time between the early termination of a signal and the time before the end of the time-frequency resource. Another shortcoming is that a SPS scheme along with a multiple user-multiple input multiple output (MU-MIMO) does not separate the need for single-user receivers such as, for example, maximum ratio combining (MRC) spatial schedulers, minimum mean square error (MMSE) schedulers, and interference rejection combining schedulers, for retransmission. Additionally, conventional hybrid SPS/PS solutions do not address the statistical use of MU-MIMO to resolve collisions and increase system capacity.
What is needed, then, is a method and system that overcomes these shortcomings in the prior art.